1. Field of the Invention
The present invention relates to a fuel system for an engine, in which a fuel pump has an integral subsystem for limiting the fluid pressure increase within the fuel supply line and injectors when the engine is shut down.
2. Disclosure Information
Fuel injected spark ignition engines present a particular challenge to automotive designers inasmuch as shut down of a fully warmed engine may cause fugitive hydrocarbon emissions upon restarting of the engine if the fluid pressure within the fuel line and injectors builds excessively due to hot soaking. U.S. Pat. No. 5,458,104 represents an attempt to solve this problem by introducing a vacuum and spring driven diaphragm pressure regulator in line between fuel pump and the engine. Unfortunately, the device of the '104 patent, being mounted externally of the fuel pump, and also having a vacuum connection to the engine's inlet manifold, may be susceptible to a failure mode in which a puncture or loss of integrity of the diaphragm results in fuel being aspirated into the engine through the vacuum connection, thereby resulting in both a loss of fuel control capability and excessive hydrocarbon emissions. Furthermore, the device of the '104 patent may cause an undesirable increase in fuel system pressure.
A fuel pump and system according to the present invention will help to prevent excessive pressure from building during a hot engine shutdown, while at the same time providing a robust system in which any leakage of the fuel pump's buffer system is confined within the pump housing.